(Reuters) - Residents in three states voted on Tuesday to decide on proposals to legalize marijuana for recreational use in a move that could spur a showdown with the federal government.

Polls show legalization is ahead in Washington and Colorado but trails in Oregon. If voters approve the measures, the states could become the first to legalize the recreational use of pot.

Each of the initiatives would see marijuana taxed and would regulate its sale in special stores to adults age 21 and older.

But the prospect of legalizing pot, which the federal government considers an illicit and dangerous drug liable to be abused, has raised concerns about how to keep stoned drivers off the roads and joints out of the hands of teenagers.

"We're risking a lot simply because people think they want to buy marijuana from a store," said Kevin Sabet, a former adviser to the Obama administration's drug policy czar.

Sponsors of the measure have raised $6 million in Washington, according to campaign finance records, and legalization backers in Colorado have pulled in almost $2 million. But a grassroots campaign in Oregon has struggled to sway voters.

Washington state and Oregon hold their elections by mail, while in Colorado voters headed to the polls on Tuesday.

Jean Henderson, 73, a retired resident of Broomfield, Colorado, said she voted to legalize marijuana.

"It's no worse than alcohol, and it's widely used in Colorado anyway," she said. "The state can benefit from the taxes rather than put people in jail."

Colorado, Washington and Oregon are among the 17 states which, along with the District of Columbia, allow medical marijuana.

BETTER CHANCE THAN CALIFORNIA?

Drug Policy Alliance Executive Director Ethan Nadelmann, whose affiliate groups have funded current and past legalization initiatives, said he was more optimistic than he was before a California legalization referendum that voters rejected in 2010.

"In this case, the polling has stayed up there. It's almost like we're seeing a surge of support for this in the final week," Nadelmann said.

A survey of 932 likely voters in Washington released on Saturday by Public Policy Polling found 53 percent support legalization, with a margin of error of 3.2 percent.

In Colorado, a recent SurveyUSA poll of 695 likely voters conducted for the Denver Post showed 50 percent in favor and 44 percent opposed. The survey had a 3.8 percent margin of error.

But in Oregon, legalization was trailing with 42 percent in favor, according to a survey of 405 likely voters by Elway Research for The Oregonian. The poll had a margin of error of 5 percent.

The initiatives in Colorado and Oregon, in addition to allowing and taxing pot sales at state-sanctioned stores, would allow individuals to cultivate plants for their own use.

The Washington measure differs in that it would ban people from growing their own pot. Unlike the other two measures, it would also create a specific blood limit on pot's psychoactive element, THC, for drivers.

Connor Barker, 19, a medical marijuana dispensary worker interviewed in Olympia, Washington, said he voted against the measure because of the restrictions on drivers. He fears they could lead to the arrest of motorists with lingering THC in their system.

"It makes the DUI regulations unfair," Barker said.

Nadelmann said the driver restriction and endorsements by such figures as John McKay, a former U.S. Attorney for the Western District of Washington state, made the measure in Washington the most likely to succeed.

A Massachusetts ballot initiative on Tuesday proposes allowing medical marijuana in that state. Voters in Arkansas are being asked whether to become the first southern state to allow marijuana as medicine.

In Montana, where voters in 2004 approved medical marijuana, voters will be asked whether to overturn a 2011 law that imposed tough restrictions on medical pot and led to the shutdown of dispensaries.